Hi!
On Tue, Apr 21, 2020 at 03:58:52PM +0100, Richard Sandiford wrote:
> > if (TREE_CODE (field) != FIELD_DECL)
> > continue;
> >
> > - sub_count = aapcs_vfp_sub_candidate (TREE_TYPE (field), modep);
> > + /* Ignore C++17 empty base fields, while their type indicates
> > + they do contain padding, they have zero size and thus don't
> > + contain any padding. */
> > + if (DECL_ARTIFICIAL (field)
> > + && DECL_NAME (field) == NULL_TREE
> > + && RECORD_OR_UNION_TYPE_P (TREE_TYPE (field))
> > + && DECL_SIZE (field)
> > + && integer_zerop (DECL_SIZE (field))
> > + && (*avoid_c17empty_field & AVOID))
> > + {
As multiple targets are affected apparently, I believe at least
aarch64, arm, powerpc64le, s390{,x} and ia64,
I think we should have a middle-end predicate for this, so that if we need
to tweak it, we can do it in one spot.
So is the following ok (of course after testing)?
2020-04-22 Jakub Jelinek <ja...@redhat.com>
PR target/94383
* calls.h (cxx17_empty_base_field_p): Declare.
* calls.c (cxx17_empty_base_field_p): Define.
--- gcc/calls.h.jj 2020-01-12 11:54:36.214416411 +0100
+++ gcc/calls.h 2020-04-22 11:44:09.037853379 +0200
@@ -135,5 +135,6 @@ extern tree get_attr_nonstring_decl (tre
extern void maybe_warn_nonstring_arg (tree, tree);
extern bool get_size_range (tree, tree[2], bool = false);
extern rtx rtx_for_static_chain (const_tree, bool);
+extern bool cxx17_empty_base_field_p (const_tree);
#endif // GCC_CALLS_H
--- gcc/calls.c.jj 2020-03-27 22:27:09.615964438 +0100
+++ gcc/calls.c 2020-04-22 11:44:17.621722376 +0200
@@ -6261,5 +6261,22 @@ must_pass_va_arg_in_stack (tree type)
return targetm.calls.must_pass_in_stack (arg);
}
+/* Return true if FIELD is the C++17 empty base field that should
+ be ignored for ABI calling convention decisions in order to
+ maintain ABI compatibility between C++14 and earlier, which doesn't
+ add this FIELD to classes with empty bases, and C++17 and later
+ which does. */
+
+bool
+cxx17_empty_base_field_p (const_tree field)
+{
+ return (TREE_CODE (field) == FIELD_DECL
+ && DECL_ARTIFICIAL (field)
+ && DECL_NAME (field) == NULL_TREE
+ && RECORD_OR_UNION_TYPE_P (TREE_TYPE (field))
+ && DECL_SIZE (field)
+ && integer_zerop (DECL_SIZE (field)));
+}
+
/* Tell the garbage collector about GTY markers in this source file. */
#include "gt-calls.h"
Jakub
